Question: Subscript in plots

Is it possible to subscript within a plot?

for example I have

this in principle is what I want but, the N is cursive while is O is not (and it's a bit shifted to the right, not right next to the [2] !???

Also I didnt find the meanings of mi(),mn(),mo(),mfenced()... in the help documentation which I stumbled across while googling.

for example in this case:

what do I need them for since without the mi it doesnt work?!

Is it possible to use latex notation within the plot options for more convenience?

BTW: When plotting a .ps or .eps the plotting device takes over all the features (like the examples above) but when using png instead it just prints the code behind it ( for example the `#mover(mi("x"),mi("~"))` ) and not would it should lead to